The price of a First-Class Mail Forever Stamp from the United States Postal Service for any large domestic letter weighing up to 1 ounce is 49 cents as of January 26, 2014. The maximum dimensions for a large letter are 11 1/2 inches long by 6 1/8 inches high.
As of January 2014, another 21 cents postage is required for every additional ounce, and international letters weighing 1 ounce or less can be mailed for $1.15. To determine the postage for international letters weighing more, locate the top menu on the USPS customer service webpage and mouse over the "Ship a Package" option. Then choose "Calculate a Price" from among the drop-down menu items.